Process of fireproofing wood.



i No. ssa-,227. Patented Feb. I9, Ism.

. H. V. SIMPSON.

-PnocEss 0F FIREPRUUFI'NG woon. (Applicatio med nec. 27, 1899.; (lplodpl.)

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I l l l WHA/S3551 Nrrnn Srarne Parent HENRY VALENTINE SIMPSON, OFLONDON, ENGLAND.

PROCESS OF FIREPROOFING WOOD.

SPECIFICATION forming part of Letters Patent N o. 668.227, datedFebruary 19, 1901. Application filed December 27, 1899. Serial No.741,725. (No specimens.)

To all whom, t may concern:

Be it known that I, HENRY VALENTINE SIMPSON, a subject of the Queen ofGreat Britain, residing in London, England, have invented certain newand useful Improvements in Processes of Fireprooiing Wood, of which thefollowing is a specification.

My invention relates to a method of treating wood for the purpose ofmaking it noninflammable or otherwise preserving it and of introducingcoloring-matter into it, if desired. According1 to the method hithertogenerally followed for these purposes the lumber to be treated isinclosed in an air-tight receptacle and then heated by direct contactwith steam or by means of internal steamcoils or hot jackets for aconsiderable time. When the wood has been sufficiently heated, a portionof the constituents are withdrawn therefrom and the pores are exhaustedof air by a vacuum-pump. Then the chemical solution is admitted andimmediately fills the empty pores. The impregnation may be assisted bypressure. This process has under certain conditions given good results;but it has been found to possess the following disadvantages-that is tosay, the direct action of heat on wood in the ordinary condition of thelatter (either as dry heat or in the form of steam) is liable to aectits structural strength, to darken its color, and to otherwise alter itscharacteristics. Moreover, the heating adds considerably both to thelength of time and to the cost of the treatment. Now my inventionrelates to the treatment of wood with solutions of the kind hereinafterstated or with other suitable solutions in such manner that betterimpregnation can be obtained than when live steam or hot air is used incontact with the wood in its ordinary condition, as hitherto, wherebythe possibility of injuring or discoloring the wood is avoided andconsiderable economy of fuel and time is effected. Also when using thesolutions hereinafter referred to I am able to introduce into the woodinsoluble matter, so as to seal the fireproofing salts in the pores ofthe wood.

I employ a horizontal cylindrical receptacle with an opening at one orboth ends capable of being hermetically sealed by means of doors. Thecylinder and doors must be capable of withstanding from two hundred andfty to 'ing solution.

three hundred pounds hydraulic pressure per square inch. In connectionwith the cylinder I employ an air-pump for creating an exhaust, apressure-pump for obtaining the necessary pressure, and the usualconnections with tanks holding the impregnating solution.

The accompanying drawing illustratesI diagrammatically an apparatussuitable for carrying out my invention.

In the drawing, A is a horizontal c ylindrical receiver provided at oneend with an opening adapted to be sealed hermetically by means of a doora. The' cylinder and door must be capable of withstanding from twohundred and fifty to three hundred pounds hydraulic pressure per squareinch. The receiver A is provided with a safety-valve b', thermometer c,vacuum gage d, pressuregage e, and blow-off cock f. Within the receiverA are longitudinal rails h, uponwhich the timber 1l to be treated can berun iin on carsj.

B is a vacuum-pump for exhausting the receiver through the pipe h, whichpipe is litted with a cock l to open and close communication with thereceiver.

C is a pressure-pump communicating with the receiver through a pipe c',adapted to be opened or closed by a cock 2. This pump 'serves to putpressure on the contents of the receiver when required.

D is a tank for containing the impregnat- One tank only is shown; but itwill be understood that several may be enlployed. Pipes d d2 d3, adaptedto be closed by cocks 3, i, and 5, serve to conduct the impregnatingsolution from the tank D to the receiver.

E is a boiler for supplying steam to the Ieceiver A when requiredthrough the pipe e', which is adapted to be closedby a cock 6.

E is a pump for drawing the solution from the receiver when so desiredand returning it to the tank D by the pipes ff2.

7 is a cock in the pipef', adapted to open or close communication withthe pump F.

Thewood to be treated (which can be of the ordinary trade sizes anddescriptions) if very wet may be first dried to some extent and isplaced on the cars j, which run on the rails h into the cylinder A. Thedoor ais then closed and the solution admitted into IOO Aill eifects,for when the Wood has been pregwise.

.the cylinder through the pipes d d2 d3 until the latter is full.Pressure is then applied by the pump C for the necessary time-say tenhours-which depends on the character and dimensions of the Wood. Thesolution is then returned to the tank D by the pump F.

In the case of soft wood of slight thickness, such as pine one inch totwo inches, matchboarding, electric-wire casing, and veneering, theabove-specified time will be found sufficient to effect saturation, andthe wood can then be withdrawn, and as no steam or other heat has beenused the Wood will not be affected in respect of its color or other-Such Woods as one-inch pine I find can be saturated with three hundredpounds pressure in three to six hours. I'n the case of hard woods Iprefer a pressure exceeding three hundred pounds, in which case thereceiver must be correspondingly strong.

In the case of the harder kinds of wood or greater thicknesses of softwood only a partial impregnation will have been effected by the aboveoperation, and I therefore continue the treatment as follows, viz: Whenthe Wood is partially impregnated, as above described, the cylinder Amay or may not be exhausted by means of the vacuum-pump B. Sufficientlive steamis then led into the cylinder from the boiler E to causeebullition of the solution already in the wood. When the vacuumpump isemployed, this ebullition takes place at a low temperature, and the woodis therefore not subjected to an injurious temperature. The effect ofthis ebullitiou of the solution in the wood is to render the woodamenable for further impregnation. When this ebullition has continuedfor, say, three or four hours, the steam is cut off (the vacuum beingmaintained) and the solution is again admitted to the Wood underpressure of the pump O, when the wood will be found to take up aconsiderably-increased quantity of the solution. In the case of verythick or very hard woods this further treatment may be 'advantageouslyrepeated.

In certain cases I may heat the wood, as above described, withoutcreating a vacuum. The ebullition will then take place at the ordinarytemperature of boiling water Without viously partially impregnated eventhis great heat does not appear to affect it. A characteristic featureof this method is the application of heat to the Wood only after it hasbeen partially impregnated with the solution without heat. There are twowell-known methods or processes of impregnation. One of these is knownas the double-solution method and consists in impregnating the wood bysuccessive solutions Which cause a reaction on meeting, therebyfireproofing the wood and precipitating in the Wood insoluble matterwhich cannot be washed out. The disadvantage of this process is thelength of time required, the extensive apparatus, and the considerableprecipitation formed on the outside of the wood, causing Waste and anunsightly appearance and also injury to any tools that maybe used inworking the Wood thereafter. The other, or the single-solution method,consists in using ireproof ingredients which are sollible in Water, theWood being impregnated with the solution and the Water being driven off`by evaporation, leaving the salts in the Wood.v The disadvantage of thesingle-solution method is that the ingredients employed, beingnecessarily soluble in Water, are liable to be Washed out on exposure tothe Weather, orif the Wood is subjected to washing` or scrubhing theWood is also liable to absorb moisture, so that it will corrode metalsand will be in other respects inconvenient. Now the ingredients of thesolution lem ploy and their proportions are such that I can introduce,as already stated, a desirable proportion of insoluble matter into thewood in a single solution, thus affording practically all the advantagesof both the double and single solution methods Without any of thedisadvantages appertainin'g thereto. In order to obtain this desirableresult, I make use of the property possessed by the combination ofcertain salts which, although soluble in water at a certain strength,will, on the strength of the solution being increased by the evaporationof the water or other volatile matter, crystallize out as insolubleprecipitates. As an example, I may mention the combination of phosphateof ammonia, sulfate of ammonia, and sulfate of zinc in certainproportionssay six, six, and two-in solution with water at a certainstrength ofsolution-say sixteen per cent. The wood isimpregnated, asabove referred to, with this solution, then the Water of the solution isdriven off from the wood by evaporation either in the open air or inkilns, and so the solution in the Wood gets stronger, causing eventuallya considerable quantity of an insoluble precipitate. of probablyphosphare of Zinc or some compound salt to form throughout the saturatedpart of the wood, and so sealing the ammonia salts in the pores of thewood. If the solution is used cold and no heat used in the drying offthe water of the solution, the sulfate of ammonia may be omitted.Another example is a solution of phosphate of ammonia, sulfate ofammonia, and sulfate of magnesia in the proportions of six, six, andone. In this case the result may be assisted by the formation ofphosphate of magnesium, which would take place if any ammonia be setfree in the dry rooms or kilns. Still another example is a combinationof sulfate of ammonia, sulfate of zinc or of magnesia, and boracic acidin the proportion of ten, six, and four, the boracic acid forming borateof zinc or of magnesia, which is crystallized in the wood on thestrength of the solution being increased by evaporation. In order toprevent this last-mentioned solution becoming too acid, I may add asmall proportion of potash or other suitable alkali thereto or combineborax therewith. I find the pro- IOC portion of insoluble matter thusformed is, in the above-specied porportions, sufficient to effect mypurpose of rendering Wood Waterresisting or non-absorbent,`noninammable,and non corrosive. The proportion may under circumstances depending` onthe nature Vof the Wood and the method of impregnation be somewhatvaried.

When coloring-matter is to be introduced into the Wood, it may be addedto the solution used for rendering the Wood non-inflam- Inable, or ifthe Wood is to be colored only1 and not rendered non-inflammable acolored solution of any knoWn constituents may ,be used instead of thenon-inflammable solution.

I claim as luy-invention the following-defined novel features,substantially as hereinbefore specified, namely:

l. A method of treating Wood to render it non-inflammable byimpregnation With a single solution, characterized by impregnating WoodWith a solution of ammonium salt and metallic salt, said salts beingsoluble at a certain strength, but Whicli,\vhen the strength of thesolution is increased react and deposit an insoluble precipitate in thepores of the wood Which precipitate seals the non-infiaminableingredients therein.

2. A method of treating Wood to render it non-inflammable byimpregnation With a single solution, characterized by impregnating thewood with a single solution of sulfate of ammonia, phosphate of ammonia,and a metallic salt, said salts being soluble at a certain strength ofsolution but reacting When the strength of the solution is increased, toproduce an insoluble precipitate, then removing suiticient of thesolvent to cause the i deposit of said insoluble precipitate in thepores of the Wood, whereby said insoluble precipitate seals thenon-iniiammable salts in the pores of the Wood.

3. A method of treatingn Wood to render it non-inflammable byimpregnation with a single solution, characterized by impregnating theWood With a single solution of sulfate of ammonia, phosphate of ammoniaand sulfate of zinc, and then removing sufficient of the solvent tocause the deposit of an insoluble precipitate in the pores of the Woodto seal the non-iniiammable salts therein.

4. A method of treating Wood to render it non-in flammable byimpregnation With a single solution, characterized by irst impregnatingthe Wood, before the application of heat, With a solution ofingredients, Which ingredients are soluble at a certain strength, butwhich, When the strength of the solution is increased, react and depositan insoluble precipitate, then subjecting the Wood to the action of livesteam so as to increase the absorptive powers of the Wood for thesolution, then again applying the same solution to the Wood toimpregnate it to the required depth, and finally removing sucient of themoisture to cause the deposit of said precipitate to seal thenon-indammable salts in th pores of the wood.

5. A method of treating Wood to render it non-in flammable, byimpregnation With a single solution, characterized by first impregnatingthe Wood, before the application of heat, with a single solution ofsulfate of ammonia, phosphate of ammonia and sulfate of zinc, thensubjecting the Wood to the action of live steam so as to increase theabsorptive power of the Wood for the solution, then again applying thesame solution to the Wood to impregnate it to the required depth, andfinally removing sufficient of the moisture to cause the deposit of theinsoluble precipitate to seal the non-inammable salts in the pores ofthe Wood.

6. The method of treating Wood for rendering :it non-iniiammable and forother purposes, Which consists in depositing in the Wood substanceswhich are non-inflammable and insoluble in Water, then subjecting theWood to the action of live steam, and then further depositing in theWood substances which are non-iniiammable and insoluble in Water.

7. The method of treating Wood for rendering it non-inflammable byimpregnation with a single solution, Which consists in impregnating itWith a solution composed of a mixture of salts Which are soluble inwater at a certain strength of solution but Which produce an insolubleprecipitate When the strength of the solution is increased byevaporation, and subsequently treating the Wood to evaporate suchimpregnated solution and thereby effect suoli precipitation in the poresof the Wood.

In Witness whereof I have hereunto signed my name in the presence of twosubscribing Witnesses.

HENRY VALENTINE SIMPSON.

Witnesses:

ARTHUR C. FRASER, FRED WHITE.

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